1. Field of the Invention
The disclosures herein relate to an image forming apparatus.
2. Description of the Related Art
Image forming apparatuses provided with an ADF (i.e., auto document feeder) and/or a CIS (i.e., contact image sensor) have been used in recent years. A CIS is provided in a scanner unit, and is capable of scanning both sides of a document sheet generally at the same time. An image forming apparatus equipped with a CIS tends to consume more electric power than an image forming apparatus that scans both sides of a document sheet by reversing the sheet. This is because the CIS includes a plurality of image sensors.
Further, image forming apparatuses have been configured such that various optional units such as a paper feed tray or a finisher may be utilized. There is thus concern about an increase in power consumption due to the use of various optional units.
Japanese Patent Application Publication No. 2009-111909 discloses an image forming apparatus that achieves power saving by suspending power supply to a CIS depending on the scan mode.
An image forming apparatus includes a fuser unit. The fuser unit applies pressure or both heat and pressure to toner transferred onto a sheet, thereby causing the toner to be fused to the sheet.
The image forming apparatus disclosed in the above-noted patent publication adjusts power supply to the CIS depending on the image quality mode which is specified for a scanned image (hereinafter referred to as a “scanned-image quality mode”). Specifically, a large amount of electric power is supplied to the CIS upon determining that the scanned-image quality mode is set to a high quality mode. This is because an increased number of image sensors need to be used in the CIS in such a case. Conversely, a small amount of electric power is supplied to the CIS upon determining that the scanned-image quality mode is set to a low quality mode. This is because a decreased number of image sensors may be used in the CIS in such a case.
In the image forming apparatus disclosed in the above-noted patent publication, however, the amount of power supply to the fuser unit may be decreased when an increased number of optional units are used because these optional units consume electric power. Reduction in power supply to the fuser unit may cause a drop in the speed of image formation.
Accordingly, it may be desirable to provide an image forming apparatus that can prevent, to a maximum extent, reduction in power supply to the fuser unit even when a number of optional units used with the image forming apparatus is increased, thereby preventing a drop in the speed of image formation.